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Que. Which of the following DMA transfer modes and interrupt handling mechanisms will enable the highest I/O band-width?
a. Transparent DMA and Polling interrupts
b. Cycle-stealing and Vectored interrupts
c. Block transfer and Vectored interrupts
d. Block transfer and Polling interrupts
Answer:Block transfer and Vectored interrupts
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Consider a set of n tasks with known runtimes r1, r2, .... rn to be run on a uniprocessor machine. Which of the following processor scheduling algorithms will result in the maximum throughput?
We wish to schedule three processes P1, P2 and P3 on a uniprocessor system. The priorities, CPU time requirements and arrival times of the processes are as shown below.

 Process  Priority  CPU time required  Arrival time (hh:mm:ss)
 P1 10(highest)  20 sec  00:00:05
 P2  9  10 sec  00:00:03
 P3  8 (lowest)  15 sec  00:00:00

We have a choice of preemptive or non-preemptive scheduling. In preemptive scheduling, a late-arriving higher priority process can preempt a currently running process with lower priority. In non-preemptive scheduling, a late-arriving higher priority process must wait for the currently executing process to complete before it can be scheduled on the processor. What are the turnaround times (time from arrival till completion) of P2 using preemptive and non-preemptive scheduling respectively.
Using a larger block size in a fixed block size file system leads to :
In a particular Unix OS, each data block is of size 1024 bytes, each node has 10 direct data block addresses and three additional addresses: one for single indirect block, one for double indirect block and one for triple indirect block. Also, each block can contain addresses for 128 blocks. Which one of the following is approximately the maximum size of a file in the file system?
A process has been allocated 3 page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): 1, 2, 1, 3, 7, 4, 5, 6, 3, 1 If optimal page replacement policy is used, how many page faults occur for the above reference string?
Fetch_And_Add(X,i) is an atomic Read-Modify-Write instruction that reads the value of memory location X, increments it by the value i, and returns the old value of X. It is used in the pseudocode shown below to implement a busy-wait lock. L is an unsigned integer shared variable initialized to 0. The value of 0 corresponds to lock being available, while any non-zero value corresponds to the lock being not available.

AcquireLock(L){
while (Fetch_And_Add(L,1))
L = 1;
}
ReleaseLock(L){
L = 0;
}

This implementation
Consider Peterson’s algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below.

repeat
flag [i] = true;
turn = j;
while ( P ) do no-op;
Enter critical section, perform actions, then exit critical
section
flag [ i ] = false;
Perform other non-critical section actions.
until false;

For the program to guarantee mutual exclusion, the predicate P in the while loop should be.
Which one of the following is NOT shared by the threads of the same process?
Consider a paging hardware with a TLB. Assume that the entire page table and all the pages are in the physical memory. It takes 10 milliseconds to search the TLB and 80 milliseconds to access the physical memory. If the TLB hit ratio is 0.6, the effective memory access time (in milliseconds) is _________.
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